<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>关于em在Css中的计算</title>
	<style type="text/css">
		html {
			font-size: 100%;
		}
		body {
			font-size: 1em;
		}
		#wrap {
			width: 46.25em;/*740px ÷ 16 = 46.25em */
			margin: 1.5em auto;/*24px ÷ 16 = 1.5em*/
			border: 0.0625em solid #ccc;/*1px ÷ 16 = 0.0625em*/
		}
	</style>
</head>
<body>
	<div id="wrap"></div>
</body>
</html>